Mobile electronic devices have become ubiquitous in today's fast paced society. Various portable or mobile handheld devices can perform multiple tasks as well as provide multiple communication systems. For example, the personal digital assistant (“PDA”) cellular telephone, in addition to serving as a personal organizer and cellular phone, may also provide text messaging, paging, and Internet connectivity. Accordingly, most devices require an interface for entering alphabetic as well as numeric characters.
Mobile devices, such as a simple cellular telephone, may include a conventional 12-key telephone keypad (also known as an alphanumeric keypad), having 10 keys associated with the numeric values 0-9 and two additional keys associated with an asterisk and pound symbol. Several methods have evolved for entering text on the telephone keypad, for example, multi-tap or predictive text entry (e.g., T9 Text Input™ by America Online, Inc., of Dulles, Va.). Despite such methods, entering alphabetic characters via a typical 12-key telephone keypad may remain inefficient for users because the inherit multifunction nature of the alphanumeric keys does not allow for easy identification of the selected character. Typically, the user must look at a display that is usually backlit to determine the character selected; however, depending on the ambient light the display may not be clearly visible to the user.